Strip tracking alarm



P. H. M CONAGHEY STRIP TRACKING ALARM Filed June 18, 1951 Sept. 1, 1953 H a m M mm W mNAmW mo 3 wfi W um Pwm MA H Patented Sept. 1, 1953 STRIP TRACKING ALARM Philip H. McConaghey, Pittsburgh, Pa., assignor to United States Steel Corporation, a corporation of New Jersey Application June 18, 1951, Serial No. 232,233 3 Claims. (c1; 340-259) This invention relates to an improved device for warning when a metal strip moving in a processing line is tracking improperly.

An object of the invention is to provide an improved device which warns of improper tracking of obscured portions of a strip, such as portions passing through a continuous annealing furnace.

A further object is to provide an improved warning device which is electrically operated and furnishes both a visual and an audible signal when a strip tracks improperly to either side.

In accomplishing these and other objects of the invention, I have provided improved details of structure, a single form of which is shown in the accompanying drawing, in which:

The single figure is a schematic plan view and a circuit diagram of a warning device which embodies features of the present invention.

The drawing shows in plan a portion of a con tinuous strip S traveling in a processing line. Somewhere in its length the strip passes over an electrically grounded roll II]. In accordance with the present invention, contact plates I2 and I2a are fixed at opposite sides of the strip in positions where the strip clears them as long as it tracks properly, but contacts one of them whenever it commences to track improperly. In practice such contact plates are situated wherever visibility of the strip is obscured, such as in an annealing furnace.

The warning device comprises an electrically operated audible signal I3, such as a siren or bell, and an electrically operated visual signal I4, such as a lamp. The operating means for the signals I3 and I4 includes a relay A, which has a set of contacts I5, a second relay B, which has a set of contacts I6, and a step-down transformer II. The contacts I5 and I6 both are normally closed; that is, when their relays are not energized, they are closed and the relays must be energized to open them. However, when the strip is tracking properly, both relays are energized and these contacts are open.

The electric operating circuit includes power lines I8 and I9 connected to a suitable A. C. source and to the primary coil of the transformer I'I. Preferably these lines contain a master switch 20. A conductor 2| connects line I8 to one contact of each of the sets I5 and I6 and to one end of the coil of relay A. A conductor 22 connects the other contact of set I5 with one side of the audible signal I3. A conductor 23 connects the other side of signal I3 with the line I9. A conductor 24, containing a resistance 25,

connects both the other contact of set I6 and the other end of the coil of relay A with conductor 23 and thus with line I9. It is seen that contacts I5 are in series with the audible signal I3 so that, when they are closed, this signal is actuated. It is also seen that contacts I6 are in parallel with the coil of relay A. As already mentioned, when the strip is tracking properly, relay B is energized and its contacts I6 are open. Consequently cur rent flows through the coil of relay A, energizes this relay and holds its contacts I5 open. When contacts I6 are closed by improper tracking of the strip, as hereinafter explained, they shortcircuit the coil of relay A, which then does not receive enough current to remain energized and hence its contacts I5 close and actuate signal I3.

A conductor 26 connects one end of the secondary coil of the transformer with one end of the coil of relay B. A conductor 21 connects the other end of this coil with one side of the visual signal I4 and is grounded at 28. A conductor 29 connects the other side of signal I4 with the other end of the secondary coil of the transformer. When the strip is tracking properly, the coil of relay B thus receives current from the secondary coil of the transformer. The electrical resistance of the coil of relay B is suinciently great that not enough current flows to actuate the visual signal I4. A conductor 30 connects both of the plates I2 and I2a with conductor 26.

Assume now that strip S contacts one of the plates I2 or [2a. A low resistance current path is thereby established from the secondary coil of the transformer I'I via conductor 30, the plate I2 or I2a, the strip S, the grounded roll III, the grounded conductor 28, conductor 21, the visual signal I4, and conductor 29, back to the sec ondary coil. The current which now flows is sufficient to actuate the visual signal I4. The ground also short-circuits the coil of relay B, which no longer receives suflicient current to remain energized; consequently its contacts I6 close and short-circuit the coil of relay A to actuate the audible signal I 3, as already explained. Both the visual and the audible signals remain actuated as long as the strip contacts one of the plates and thus give a continuous warning of improper tracking until that condition is corrected.

The device is particularly suited for use in a continuous annealing furnace, where view of the strip is obscured by the furnace enclosure. In such furnaces improper tracking of the strip can damage not only the strip, but also the furnace.

3 In electrically heated furnaces, if the strip tracks improperly, it can cut into the heating elements and short-circuit the entire furnace.

While I have shown and described only a single embodiment of the invention, it is apparent that modifications may arise. Therefore, I do not wish to be limited to the disclosure set forth but only by the scope of the appended'clai'ms.

I claim:

l. A device for warning when a metal strip tracks improperly comprising a ground connected to the strip, a contact plate whicl the-stnip normally clears but is adapted to contact when tracking improperly, a visual sig'nal, fan'audible signal, and an electric circuit 'ihcludingapairbf relays and a step-down transformer having power lines connected to its primary-coil, the contacts of one of relays and one of said signals being connected in series across said lines, the'c'oil of this relay also being connected across these une the contacts -c f the second reiay being cea jnectedin parallel with the 'coil"of the firstrela-y, the coil of the second relayand the -other signal being connected in series "a'c ross the secondary -coil of said transformer, said"contact plate be "ing connected between the secondary coil of 'said transformer 1 and the coil of the second relay,

the 'connectionbetween the coil ofthesecond relay a'ndsaidsecond signal 'being'g'ioiirid'ed, both relays being energizedwhenthe strip is tracking' properly and holding their'ccntacts open,con

tact by the stripwith said contact plate short- 2. A device for 'warning'whenametalstrip tracks improperly comprisinga ground connect- "ed'to the strip, a pair of contact plates on oppo- "site sides of' the strip'w'hich the strip normally clears but is adapted to contact whentrackin'g improperly, a visual signaLanaudible signal, and an I electric circuit including a" pair of relays and a" step-down transformer havingpower lines connected-to its primary coil, the contacts'of'one of said relays and said audible signalbeing connected in series across said lines, the coilof'this relayalso being connectedacross these lines," the "contacts of the second'relay beingconnecte'dfii parallel with the coil of the first relay, the "coil of the second relay and said visual signal being connected in series across the secondary coil of said transformer, said contact plates being connected between the secondary coil of said transformer and the coil of the second relay, the connection between the coil of the second relay and said visual signal being grounded, both relays being energized when thefstrip is tracking properly and holdingtheir-contacts open, contact by the strip with one of said contact plates shortc'ircuiting the coil of the second relay through the ground and thereby de-energizing this relay, actuating "said visual signal, short-circuiting the -"o the rst relay, (lo-energizing this relay g -said audible signal. 39A device-for warning when a metal strip tracks improperlycomprising a ground connected to the strip, a plate which the strip normally clearsythe space between said plate and the strip being unobstructed to enable the strip to engage "the=-plate as it shifts 'side'wi'se when" tracking imwproperly, I firstand sec'ondrelays each of which includes a'coiland a-set-of normally closed contacts, '-a first-signal connected in "series with the -contacts 'of-"sai'd' first relay, a second signal 'con- -nected inseries -with'the *coilof said second relay with: a ground connected 'therebetw'ee'n, the contacts of said second relay being connected in parallel"with=the co'ilof said first relay, said plate fbeing connected' to the coil or said second relay "on t'he"opp'0site side fromsaid second named 'ground;'-'and an"electr'ic"circ1iit normally energizmgsaidreIays and holdingtheir contacts open toprevent-eriergization" offsaid signals; engage- =inent of said plate by-thestr'ip short-circuiting said second relay-to -deenergizethe relays "and eriable' sa'id circuit *to energize' said signals.

PHILIP HS McCONAGI-IEY. 

